Testing of intermediate range nuclear instruments is conventionally conducted at a test facility with simulated current which represents reactor power. Intermediate range nuclear instruments tested in this way include, for example, the Weston S5W microelectronic (a discrete analog integrated circuit), the Westinghouse S6W microprocessor, and the Sorrento S6W microprocessor. During such testing, it has been found that an interface is required between the hybrid computer reactor simulation used in carrying out the test and the intermediate range nuclear instrument being tested.
It has been found that, ideally, the interface between the hybrid computer and the nuclear instrument would comprise a current source that receives as an input from the hybrid computer a voltage which represents the logarithm of core power, and produces as an output a real time, continuously variable current having a range of from 10 picoamperes to 100 microamperes. A real time current output is necessary in order for operational simulations to be performed, and a continuously variable current is required to avoid discontinuities in current which would otherwise invalidate the test results. Commercially available current sources do not satisfy the above criteria, especially in terms of providing a continuously variable current over a seven decade range.